\(B=\left(1-\frac{1}{2}\right).\left(1-\frac{1}{3}\right).\left(1-\frac{1}{4}\right)...\left(1-\frac{1}{2003}\right).\left(1-\frac{1}{2004}\right)\)
\(B=\frac{1}{2}.\frac{2}{3}.\frac{3}{4}.....\frac{2002}{2003}.\frac{2003}{2004}\)
\(B=\frac{1.2.3.....2002.2003}{2.3.4.....2003.2004}\)
\(B=\frac{1}{2004}\)
B = (1 - 1/2).(1 - 1/3).(1 - 1/4).(1 - 1/5)...(1 - 1/2003).(1 - 1/2004)
B = 1/2 . 2/3 . 3/4 . 4/5 .... 2002/2003 . 2003/2004
B = 1.2.3.4...2002.2003/2.3.4.5...2003.2004
B = 1/2004